Spark gap

ABSTRACT

A spark-gap device is disclosed which comprises an envelope forming a gas-filled space. The space accomodates electrodes; namely, a cathode and an anode. The inter-electrode space accomodates a bushing of dielectric material attached to one of the electrodes. The bushing is provided with at least one duct made in the body of the bushing so that the spark discharge occurring between the electrodes passes through the duct having a constant longitudinal section.

United States Patent Belyaev et al.

[451 Aug. 13, 1974 SPARK GAP Inventors: Viktor Borisovich Belyaev, ulitsa, 4

kv. 19; Ekaterina Sergeevna Butrova, ulitsa Poletaeva 25, kv. 4; Yury Vladimirovich Kiselev, ulitsa Podgornaya 5, kv. 29; Galina Tikohonovna Pozharskaya, ulitsa Tarolkovka Porharecaya l0, kv. 45, all of Ryazan, U.S.S.R.

Filed: Jan. 29, 1973 App]. No.: 327,860

Related U.S. Application Data Continuation of Ser. No. 221,661, Jan. 28, 1972, abandoned.

U.S. Cl. 313/205, 317/62 Int. Cl. H0lj 17/02 Field of Search 313/204, 205; 317/62 [56] References Cited UNITED STATES PATENTS 2,123,333 7/1938 Hansel] 313/204 Primary Examiner-Herman Karl Saalbach Assistant ExaminerDarwin R. Hostetter Attorney, Agent, or Firm-Holman & Stern 5 7 ABSTRACT A spark-gap device is disclosed which comprises an envelope forming a gas-filled space. The space accomodates electrodes; namely, a cathode and an anode. The inter-electrode space accomodates a bushing of dielectric material attached to one of the electrodes. The bushing is provided with at least one duct made in the body of the bushing so that the spark discharge occurring between the electrodes passes through the duct having a constant longitudinal section.

2 Claims, 1 Drawing Figure SPARK GAP This is a continuation, of application Ser. No. 221,661, filed Jan. 28, 1972, now abandoned.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to gas discharge devices and, more particularly, to spark gaps used for suppression of excess voltage in electric communication lines.

2. Description of Prior Art Known in the art is a spark gap comprising a gasfilled body accommodating electrodes (a cathode and an anode), between which spark discharges take place; and, in the inter-electrode space of the gas-filled body there is a bushing made of a dielectric material, attached to one of the electrodes.

A low extinction potential of such spark gaps (about 200 V) however makes it impracticable to use them for suppression of excess voltage in electrical communication lines with remote power supply arrangements since the discharge in such spark gaps can be sustained from the remote power supply itself.

SUMMARY OF THE INVENTION The object of the present invention is to provide a spark gap having an extinction potential of 450V.

This object is achieved by providing a spark gap comprising a gasfilled body with electrodes (a cathode and an anode) secured in it, between which spark discharges take place and in whose inter-electrode space there is disposed a bushing made of a dielectric material, attached to one of the electrodes; said bushing, according to the invention, is provided with at least one duct made in its body such that the spark discharge between the electrodes passes through said duct.

The provision of one or a plurality of ducts in the bushing made of a dielectric material and incorporated in the spark gap makes it possible to raise the extinction potential up to 450 V and to reduce the size and weight of the device.

BRIEF DESCRIPTION OF THE DRAWING An embodiment of the invention will now be described by way of example with reference to the accompanying drawing which presents a longitudinal sectional view of a spark gap device of the present invention.

DESCRIPTION OF PREFERRED EMBODIMENT The spark gap device according to the invention comprises a body 1 made as a glass cylinder having fernico cups 2 welded to its butt ends. The body 1 houses tungsten electrodes, viz, a cathode 3 and an anode 4, which have copper lead-outs 5 and 6 soldered to them. The other ends of the lead-outs are soldered to the cups 2.

Mounted in the inter-electrode space between the cathode 3 and the anode 4 is a bushing 7 of a dielectric material (which in the embodiment being described is ceramics). The bushing is soldered to the lead 5 of the cathode 3 in such a manner that there are gaps between the cathode 3 and the bushing 7 and between the anode 4 and the bushing 7. The bushing 7 is provided with five ducts 8 formed at the butt end of the bushing 7 which faces the inter-electrode space. One of the ducts 8 is in the centre of the bushing 7 while the other four ducts 8 are arranged uniformly along the perimeter of said butt end of the bushing 7.

The sizes and the positions of the ducts 8 are selected and predetermined such that a spark discharge between the electrodes could take place only through these ducts 8.

It is known that the extinction potential of a spark gap depends on the balance between the power fed to the spark gap from the supply and the power which is dissipated due to heat conduction of the discharge radiation. The greater the power loss, the higher is the voltage at which the spark gap becomes balanced and, hence, the higher is its extinction potential.

The amount of power lost by the discharge column due to dissipation can increase sharply if the discharge touches the walls of the ducts 8 through which it passes. Besides, the ratio of the column surface of the discharge to its volume in narrow ducts is higher than that in broad ducts, which makes the requirement of heat removal still more important.

Since the relative power loss on the walls of the ducts 8 grows with the reduction of the duct diameter, the extinction voltage of a spark gap having narrow ducts exceeds that of a spark gap with broad ducts.

By suitably proportioning and varying the length and the diameter of the ducts 8 it is possible to obtain the required value of the extinction voltage. In is preferable however that the duct diameter should be selected within the range from 0.1 to 1.5 mm.

It is found that a duct 8 with a diameter above 1.5 mm has practically no effect on the extinction potential, while if the diameter is reduced below 0.1 mm the temperature of the plasma inside the duct during the spark discharge becomes too high for the material of the bushing 7 to withstand.

The length of the ducts 8 is selected from 0.5 to 10 mm and more, since the extinction potential of the spark gap is proportional to the duct length.

The spark gap is expediently filled with neutral gases or with hydrogen. The best neutral gases for this purpose are helium and neon.

The herein disclosed spark gap operates as follows.

The spark gap is connected between two wires of a communication line with a remote 450 V power supply and, therefore, there is always a potential difference of 450 V across its electrodes. In case an overvoltage oc curs in the line the spark gap develops a spark discharge which sharply brings down the voltage across 4 the electrodes.

After the discharge is over the spark gap restores its insulation properties since the 450V power supply cannot sustain the dischange therein due to the fact that the extinction potential of the spark gap is above 450 V. i

The present spark gap can withstand thousands of breakdowns with maximum pulse currents of up to 5,000 A.

The spark gap reliably protects communication line equipment having 450 V remote supplies, from dangerous overvoltages.

The spark gap features small size and weight.

What is claimed is:

1. A spark-gap device comprising:

a hollow body filled with a pre-selected gas medium;

a first electrode disposed in said body and forming a at least one through duct formed in the body of said cathode; bushing in the longitudinal direction thereof, said a second electrode forming an anode and disposed in at least one through duct having a pre-selected disaid body in spaced relationship with said cathode; ameter and length defining means for passing the 5 spark discharge occurring between said electrodes a spark discharge taking place in an inter-electrode through said at least one through duct.

space defined between and extending from said 2. A spark-gap device as claimed in claim 1, wherein first and said second electrodes; said at least one through duct has a constant section a bushing made of dielectric material disposed in the having a diameter between 0.1 1.5 mm and a length inter-electrode space between said electrodes and 0 between 0.5 mm and over. attached to one of said electrodes; and 

1. A spark-gap device comprising: a hollow body filled with a pre-selected gas medium; a first electrode disposed in said body and forming a cathode; a second electrode forming an anode and disposed in said body in spaced relationship with said cathode; a spark discharge taking place in an inter-electrode space defined between and extending from said first and said second electrodes; a bushing made of dielectric material disposed in the interelectrode space between said electrodes and attached to one of said electrodes; and at least one through duct formed in the body of said bushing in the longitudinal direction thereof, said at least one through duct having a pre-selected diameter and length defining means for passing the spark discharge occurring between said electrodes through said at least one through duct.
 2. A spark-gap device as claimed in claim 1, wherein said at least one through duct has a constant section having a diameter between 0.1 - 1.5 mm and a length between 0.5 - 10 mm and over. 